1. Field of the Invention
Generally, the present invention relates to a semiconductor device, and more particularly to an inexpensive semiconductor device which is improved so that noise propagation can be reduced.
The present invention also relates to a manufacturing method of such a semiconductor device.
2. Description of the Background Art
FIG. 12 is a sectional view of a conventional high frequency silicon semiconductor device. An oxide film layer 5 is formed in a silicon substrate 1. A trench isolation 6 is located on oxide film layer 5. A gate electrode 2 of a transistor is located on silicon substrate 1. Wires 3 are connected to the transistor. An interlayer insulating film 4 covers silicon substrate 1 in order to insulate the transistor and the wires.
Thus, the conventional high frequency silicon semiconductor device is fabricated with an SOI (Silicon on Insulator) wafer utilizing a silicon substrate as a base, and is also combined with an isolation technique such as a trench isolation, thereby attempting to reduce crosstalk noise. That is, there has a configuration that trench isolation 6 separates a circuit block which generates noise from a circuit block in which it is desired to suppress noise level to reduce noise propagating in silicon substrate 1.
Such a high frequency silicon semiconductor device is operated at a frequency band greater than several GHz for transmission and reception and is utilized in a cellular phone, a wireless local area network, other high rate communication equipment and the like.
The conventional high frequency silicon semiconductor device is configured as described above. Since the SOI substrate is manufactured through a complicated process sequence such as ion implantation, wafer bonding and wafer splitting, there is a demerit that the price is high in comparison with a conventional silicon substrate.
The present invention is made to solve the above described problem and an object thereof is to provide a high frequency silicon semiconductor device which is improved so as to be capable of manufacturing inexpensively.
Another object of the present invention is to provide a semiconductor device which is improved such that noise propagating in the silicon substrate can be reduced by means of an inexpensive method.
Still another object of the present invention is to provide a manufacturing method of such a semiconductor device.
A semiconductor device according to a first aspect of the present invention is provided with: a semiconductor substrate; a trench vertically penetrating through the semiconductor substrate; and a semiconductor element formed on the semiconductor substrate.
According to the present invention, a trench penetrating through the semiconductor substrate is provided, so that noise propagation via the semiconductor substrate can be reduced.
A method according to a second aspect of the present invention relates to a manufacturing method of a semiconductor device which has a semiconductor substrate through which a trench vertically penetrates is formed. First, a portion for forming the trench of the semiconductor substrate is downwardly excavated up to the middle of the substrate. An insulator is fully or partially embedded into the downwardly excavated portion. The portion for forming the trench of the semiconductor substrate is excavated from an opposite side of the substrate until the insulator appears.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.